The present invention generally pertains to secure data processing systems and is particularly directed to enhancing the security of a given data processing routine in which an essential predetermined signal is utilized.
More specifically, it is desired to enhance the security of a data processing routine in which the essential predetermined signal is a decryption key that is used for descrambling scrambled information signals.
Examples of data processing systems that utilize a decryption key for descrambling scrambled information signals are described in U.S. Pat. Nos. 4,613,901 to Klein S. Gilhousen, Charles F. Newby, Jr. and Karl E. Moerder; 4,712,238 to Klein S. Gilhousen, Michael V. Harding, Jerrold A. Heller and Robert D. Blakeney, II; and 4,864,615 to Christopher J. Bennett.